In order to drive and control an AC motor by using a DC power supply, there has been employed a drive method using an inverter. The inverter is subjected to switching control by an inverter drive circuit. For example, a voltage switched in accordance with PWM control is applied to the AC motor.
Further, Japanese Patent Laying-Open No. 2006-320039 (Patent Document 1) describes a motor drive system to which overmodulation PWM control and rectangular wave voltage control are applied as AC motor control by a modulation scheme, and the AC motor control is larger than sinusoidal PWM control with regard to a fundamental component of a motor applied voltage.
In particular, Patent Document 1 describes the following control. That is, when a motor rotation speed is changed rapidly at the time of application of the rectangular wave voltage control or the overmodulation PWM control, a voltage command value of an output voltage from a converter (i.e., an input voltage to an inverter) is changed depending on a change rate of the motor rotation speed so as to cover reduction in feedback control responsivity.